Anodizing device, continuous anodizing device, and film forming method

ABSTRACT

An anodizing device has: a power supply drum that supports, in close contact therewith, a web consisting of an anodizable metal and has a part configured with a conductive material, to which the web is closely attached; a counter electrode provided facing the power supply drum; an electrolysis tank filled with an electrolyte, into which part of the power supply drum and the counter electrode are immersed; a protection member formed of a non-conductive material that protects the lateral direction end portions of the web supported by the power supply drum in close contact therewith and a portion of the power supply drum, to which the web is not closely attached, from the electrolyte; and a driver adapted to make the web and the protection member travel concurrently in the electrolyte in synchronization with the circumferential speed of the power supply drum.

BACKGROUND OF THE INVENTION

The present invention relates to an anodizing device, a continuous anodizing device, and a film forming method suitable for producing substrates for semiconductor elements that are usefully utilized in semiconductor devices such as solar cells, thin-film transistor circuits, and displays (image display devices), and electrodes for electrolytic condensers.

Thin-film solar cells using a substrate made of a metal have a possibility of being used for various purposes compared to those using a glass substrate, in view of the lightness and flexibility of the substrate. Moreover, since the substrate made of a metal can endure a high-temperature process, photoelectric conversion characteristics are improved, and accordingly, a highly efficient solar cell can be expected.

In a solar cell module, solar cells are integrated by being connected to one another in series on the same substrate, thereby improving the module efficiency. At this time, an insulating layer needs to be formed on the metal substrate of the solar cell module, and a semiconductor circuit layer for performing photoelectric conversion needs to be disposed on the insulating layer. For example, when iron-based materials such as stainless steel are used for the substrate, it is necessary to coat the substrate with an oxide of Si or aluminum by a gas phase method such as CVD or a liquid phase method such as a sol-gel method to form an insulating layer. However, these techniques are manufacturing methods in which pinholes or cracks occur easily, and accordingly, they are fundamentally problematic as a technique for stably preparing a thin-film insulating layer having a large area (JP 2001-339081 A).

On the other hand, when aluminum is used for the substrate, a pinhole-free insulating film having excellent adhesiveness can be obtained by forming an anodic oxide film (AAO) (JP 2000-49372 A). However, the AAO on an aluminum substrate is known to crack when being heated at 120° C. or a higher temperature (Kayashima et al., Bulletin of Tokyo Metropolitan Industrial Technology Research Institute, No. 3, p. 21 (2000)) and has a problem with insulating properties, particularly, a problem of increased leakage current. Furthermore, aluminum is softened at a temperature of about 200° C., and the aluminum which suffered a temperature equal to or higher than 200° C. has an extremely low strength and easily causes permanent deformation (plastic deformation) such as creep deformation or buckling deformation. Therefore, for producing a semiconductor device by using this type of aluminum, strict restriction needs to be imposed on handling, and this makes it difficult for such production to be applied to outdoor solar cells and the like.

In order to solve the above problems, a method has been proposed in which AAO as an insulating layer is formed on a substrate made of a so-called aluminum clad material, and a compound semiconductor layer as a light-absorbing layer or an electrode layer is formed thereon. In this method, it is possible to prepare a design for reducing a difference in linear expansion coefficient between the metal substrate and the compound semiconductor layer, and even in a step of forming a compound semiconductor layer which is a film forming step performed at a high temperature of 500° C. or higher, the problems such as cracking of the insulating layer or peeling of the compound semiconductor do not arise. Moreover, since the metal base material to be combined with aluminum has a higher degree of specific strength and high-temperature strength compared to aluminum, handling of the substrate becomes easy during production of a semiconductor device.

AAO as an insulating layer needs not to cause dielectric breakdown at a high voltage when being incorporated into a cell module, and further, it needs to reduce leakage current when applied with voltage, that is, to have high volume resistance. If the leakage current is great, the current obtained by power generation becomes leakage current between cells, and the power generation efficiency of the module decreases. Accordingly, in order to secure the above performances, AAO needs to have a thickness of 1 μm or greater and preferably 5 μm or greater.

A common device used for continuously anodizing an aluminum web has a constitution in which a power supply roll or a power supply tank is disposed upstream of an electrolytic tank to supply current to aluminum, and current also flows in the aluminum extending from a power supply section to the electrolytic tank. Anodization refers to electrolytic oxidation (three-electron reaction in the case of aluminum), and the thickness of AAO is proportional to the quantity of electricity supplied. Consequently, in the device for continuously anodizing an aluminum web, current proportional to a line speed (running speed of the aluminum web) needs to be supplied. At this time, even in the aluminum extending from the power supply section to the electrolytic tank, the current proportional as above flows. Therefore, the greater the thickness of AAO is, and the higher the line speed is, the more the voltage drop increases, and this leads to power loss. Moreover, there is a possibility that the aluminum extending from the power supply section to the electrolytic tank may be fused due to IR heat generation, so there is an upper limit on the thickness of AAO to be generated and line speed. The heat generation and the limiting current of the fusing are determined depending on the resistance per unit cross-sectional area of the aluminum web. Accordingly, the thinner the aluminum foil is, the smaller the upper limit of the thickness of AAO that can be generated and the line speed is.

Meanwhile, there is a demand for forming thick AAO only on one surface of a web of thin aluminum foil, and one of the examples thereof includes the metal substrate with an insulating layer described above. In this case, it is possible to produce such a substrate using the device described above by sticking a masking film to one surface, but there is an upper limit on the thickness of AAO and the line speed. Moreover, since unlike an additive film such as plating, AAO is a subtractive film, if electrolytic solution permeates from the end face of the masking film, AAO film can be easily formed. Therefore, it is necessary to select masking film having a strong adhesive force. Furthermore, in the case of a web of metal foil obtained by joining dissimilar metals, such as a clad material, in order to prevent a side reaction caused by local galvanic action, it is necessary to also stick masking film onto the lateral end surface in the width direction in which the dissimilar metals are exposed, such that the lateral end surface becomes electrochemically inactive.

Various devices for forming AAO film only on one surface of an aluminum web have been proposed. As a typical example thereof, there is a technique in which a supporting drum having a circular cross-section is placed in an anodizing tank, and aluminum foil is caused to be in close contact with the drum so as to anodize only one surface of the aluminum foil (JP 4-371892 A). Moreover, a technique of imparting conductivity to the supporting drum and supplying power to the drum has been proposed (JP 60-211093 A). In the latter technique, since power is directly supplied from the rear surface of the aluminum foil, it is possible to reduce the extent of the voltage drop and the heat generation described above to an ignorable level.

However, in this technique, the electrolytic solution easily permeates the space between the supporting drum and the aluminum foil. In the anodizing tank, the AAO film is formed, so an over-voltage is heightened. Therefore, when the electrolytic solution permeates the supporting drum, the current which straightforwardly flows between the supporting drum and a counter electrode becomes strong, and the current for forming the AAO film in the anodizing tank undergoes current loss. Moreover, the loss current has an electrochemical action on the surface of a power supply drum that is in close contact with aluminum. As a result, anodic oxide film is also formed on the surface of aluminum that is in close contact with the drum, or when the power supply drum is made of a metal, the surface thereof is anodized or undergoes anodic dissolution. Consequently, in any case, there is a possibility that contact resistance of the surface of close contact may increase and local defectiveness such as sparking may be caused.

In order to solve the above problems, JP 60-211093 A proposes a device that uses a so-called valve metal such as tantalum or niobium as a material of the power supply drum. However, in this method, with the passage of the time of electrolytic operation, the anodic oxide film grows on the surface of the valve metal. Accordingly, since the contact resistance gradually increases, the valve metal needs to be frequently replaced, but this is unpractical due to the high cost of those materials. Meanwhile, JP 6-108289 A proposes a method of preventing the electrochemical action of the surface of close contact by supplying water to the surface of close contact between the aluminum foil and the supporting roll. Moreover, JP 46-39441 B discloses a constitution in which both ends of the aluminum foil are covered with a crimping band of a nonconductor applied with tension such that an electrolytic solution does not flow into the contact surface.

SUMMARY OF THE INVENTION

However, the device of JP 6-108289 A is complicated, and the electrolytic solution is diluted with water on the surface of close contact of the drum, so the concentration of the electrolytic solution needs to be continuously managed. Moreover, there is a possibility that when the water that forms a thin layer on the surface of close contact generates gas by electrolysis, the thin layer may become a gas layer, the contact resistance may increase, and this may lead to sparking. On the other hand, in the method disclosed in JP 46-39441 B in which the aluminum foil is covered with the band applied with tension, the band continuously slides against the power supply drum or against the aluminum foil. Therefore, the band easily strays from an end portion of the aluminum foil, and this makes it difficult to perform continuous operation. Furthermore, there is a possibility that if tension is applied by crimping, the aluminum foil may be wrinkled when it is a thin foil, and the electrolytic solution may flow into the contact surface from the wrinkled portion.

As described above, even with any of the above methods, it is impossible to completely prevent the formation of anodic oxide film on the side of the surface of close contact. Therefore, the problem with the fact that the contact resistance becomes unstable cannot be solved.

The present invention has been made in consideration of the above circumstances, and a first object of the present invention is to provide an anodizing device and a continuous anodizing device having a small contact resistance, and a film forming method using such an anodizing device or continuous anodizing device. Moreover, in addition to the first object, the present invention aims to provide a film forming method for further decreasing contact resistance and further reducing change in the contact resistance, as a second object.

As described above, various devices for forming AAO film have been proposed in the prior art. However, they have problems in that the heat generated along with anodization cannot be efficiently removed out of the system, a heat generation/temperature distribution arises in the system, the reaction becomes uneven in the anodized surface, and as a result, burning of the anodic oxide film, ununiformity of the thickness of the anodic oxide film, and the like arise.

Moreover, the various devices for forming AAO film that have been proposed in the prior art as described above have problems in that due to rotation of the drum, movement of the foil, stirring of the electrolytic solution, or hydrogen gas produced by anodization, the level of the surface of the electrolytic solution is not maintained at a constant height, and accordingly, the range of anodization continuously changes, the thickness of the anodic oxide film becomes partially uneven, and the surface of the anodic oxide film is roughened.

As a solution to the above problems, the present invention aims to provide a film forming method for forming film having a high degree of film thickness uniformity and an excellent surface condition, as a third object.

Furthermore, as described above, various devices for forming AAO film have been proposed in the prior art, and JP 60-211093 A proposes a method of imparting conductivity to the supporting drum and supplying power to the drum so as to directly supply power from the rear surface of metal foil (aluminum foil).

In the device for forming AAO film, as a method of supplying current to the anodized surface of the metal foil, there is a method of supplying current from the drum shaft to the drum surface and then to the metal foil in this order, or a method of directly supplying power to the metal foil. The former method in which supply of current is performed through the drum shaft has problems in that a bearing mechanism of the drum becomes complicated, and there is an upper limit on the current that can be conducted by the drum shaft. The latter method that directly supplies power to the metal foil has problems with Joule heat generation and limiting current since current flows inside the metal foil.

In addition, as described above, the thicker the AAO is, and the higher the line speed is, the more the voltage drop increases, whereby power loss occurs. Moreover, there is a possibility that the aluminum extending from the power supply section to the electrolytic tank may be fused due to IR heat generation, so there is an upper limit on the thickness of AAO to be formed and on the line speed. The heat generation and the limiting current of the fusing are determined depending on the resistance per unit cross-sectional area of the aluminum web. Consequently, the thinner the aluminum foil is, the smaller the upper limit of the thickness of AAO that can be generated and the line speed is.

In the device for forming AAO film, as the portion of the metal foil (aluminum foil) dipped into the electrolytic solution widens as much as possible, the productivity increases. Moreover, if the rotating shaft is placed in a position below the surface of the electrolytic solution, more than half of the drum can be used, whereby the production efficiency becomes good. However, the method of supplying power through the rotating shaft of the drum has a problem in that it is difficult to place the rotating shaft in a position below the surface of the electrolytic solution.

As a solution to the above problem, the present invention aims to provide a film forming method that can supply power by using a simple constitution, as a fourth object.

In order to achieve the first object of the present invention, it is desirable that the anodizing device has a power supply drum which is in close contact with a web made of an anodizable metal or a web made of composite conductive metal foil with at least one surface comprising an anodizable metal and as such supports the web in a state where the web is being wound around the power supply drum, and in which at least a portion that is in close contact with the web is constituted of a conductive material; a counter electrode that is disposed to face the power supply drum; an electrolytic tank that is filled with an electrolytic solution into which a portion of the power supply drum which is in close contact with and supports the web and the counter electrode are dipped; a protective member made of a nonconductive material that overlaps an end portion in a short-length direction of the web that is supported by the power supply drum in close contact with the web and a portion of the power supply drum that is not in close contact with the web so as to protect the portions from the electrolytic solution; and a driver that causes the web which is in close contact with the power supply drum and the protective member to run together in the electrolytic solution in synchronization with a circumferential speed of the power supply drum, and that, provided that a tension per width that is applied to the web wound around the power supply drum is represented by T (N/m) and a radius of the power supply drum is represented by R (m), a value of the tension T per width that is applied to the web caused to run together in the electrolytic solution is 1,000×R or greater. It is more desirable that the tension T (N/m) per width applied to the web has a value ranging from 1,000×R to 10,000×R.

In order to achieve the second object of the present invention, in addition to the application of a tension desirable for achieving the first object, it is desirable that the surface of the portion that is in close contact with the web be constituted of an electron conductive inorganic compound.

It is preferable that the electron conductive inorganic compound be at least one out of carbon or graphite, iridium oxide, titanium nitride, titanium carbide, titanium carbonitride, silicon nitride, silicon carbide, and silicon carbonitride. In the power supply drum, it is preferable that an underlayer of the surface of the portion which is in close contact with the web be constituted of metal, and the metal of the underlayer be an anodizable metal. The anodizable metal is preferably aluminum.

In order to achieve the third object of the present invention, a circulator for the electrolytic solution used in the film forming method for achieving the first and second objects is desirably a circulator adapted to move the electrolytic solution present in a gap between the counter electrode and the web which is supported by the power supply drum in close contact with the web out of the gap.

It is preferable that the circulator move the electrolytic solution present in the gap in a direction approximately in parallel with the longitudinal direction of the web.

It is preferable that the counter electrode is provided with an opening portion, and the circulator supply the electrolytic solution to the gap between the counter electrode and the web which is supported by the power supply drum in close contact with the web through the opening portion.

It is preferable that the circulator discharge the electrolytic solution in the gap in a direction approximately in parallel with the longitudinal direction of the web.

It is preferable that a cover member that blocks a second opening in a direction of a rotating shaft of the power supply drum among openings of the gap be provided, and by the circulator, the electrolytic solution in the gap be discharged from a first opening which is in a direction approximately in parallel with the longitudinal direction of the web among the gaps.

It is preferable that the cover member be fixed to the electrolytic tank or the counter electrode. Moreover, it is preferable that the cover member be fixed to the rotating shaft of the power supply drum or be relatively rotatable.

It is preferable to provide a permeation preventer adapted to prevent the electrolytic solution from permeating an opened area that faces an area where the web is wound around the power supply drum.

It is preferable that the permeation preventer have a roller that comes into contact with a second surface of the web opposite with a first surface in contact with the power supply drum, or have a blade member that comes into contact with the second surface.

It is preferable that the rotating shaft of the power supply drum be placed in a position below the liquid surface of the electrolytic solution.

In order to achieve the fourth object of the present invention, in the film forming method for achieving the first, second, and third objects, it is desirable to provide a power supplier adapted to apply current to the web, the power supplier being disposed in a position above the liquid surface of the electrolytic solution.

It is preferable that the power supplier have a first power supply member that comes into contact with the metal portion of the power supply drum.

Moreover, it is preferable that the power supplier have a second power supply member that comes into contact with the web. In this case, it is preferable that the second power supply member come into contact with the web such that the web is interposed between the second power supply member and the metal portion of the power supply drum.

It is preferable that the first and second power supply members be metal rolls or carbon rolls. Furthermore, it is preferable that the first and second power supply members be metal brushes or carbon brushes.

It is preferable to provide a permeation preventer adapted to prevent the electrolytic solution from permeating an opened area that faces an area where the web is wound around the power supply drum. It is preferable that the permeation preventer have a roller that comes into contact with a second surface of the web opposite with a first surface in contact with the power supply drum, or have a blade member that comes into contact with the second surface.

It is preferable that the roller that comes into contact with the second surface or the blade member that comes into contact with the second surface be disposed either at a surface of the electrolytic solution where the web comes into contact with the electrolytic solution or a surface of the electrolytic solution where the web is separated from the electrolytic solution, or at both the surfaces.

It is preferable that the rotating shaft of the power supply drum be placed in a position below the liquid surface of the electrolytic solution.

Regarding the first to fourth objects, it is preferable that a concavity in which the web runs while coming into contact with the inside thereof be disposed in the power supply drum. A guide roller that presses the protective member against the power supply drum may also be provided. It is preferable that the counter electrode has a large number of through-holes.

Regarding the first to fourth objects, it is preferable that the interval between the power supply drum and the counter electrode be larger either in a region where the web supported by the power supply drum comes into contact with the electrolytic solution or a region where the web is separated from the electrolytic solution, or in both the regions, than that in a central region where the web is dipped into the electrolytic solution.

Regarding the first to fourth objects, it is preferable that the protective member comprise nonconductive rubber or metal foil which is covered with nonconductive rubber. Moreover, it is preferable that the protective member have an adhesive material on a side which comes into close contact with the web.

Regarding the first to fourth objects, it is preferable that a potential of the counter electrode exhibit a negative polarity against ground. Particularly, it is preferable that a potential of the web be equal to a potential of the ground, and a power source for electrolysis used in anodization be an output insulated from the ground. It is more preferable to provide a monitor adapted to monitor a voltage of the power supply drum with respect to the potential of the ground.

In the continuous anodizing device for achieving the first to fourth objects, a large number of anodizing devices using the film forming method for achieving the first to fourth objects are arranged in series. In the film forming method of the present invention, the anodizing device or the continuous anodizing device, both adapted to achieve the first to fourth objects, is used to form anodic oxide film on one surface of the web.

Regarding the first object of the present invention, a constitution is used in which provided that a radius of the power supply drum is represented by R (m), the web wound around the power supply drum is applied with a tension (N/m) of a value of 1,000×R or greater per width and caused to run together in the electrolytic solution, thereby reducing the contact resistance of the web. Accordingly, it is possible to suppress power consumption and cost of power and thus to reduce production cost. Moreover, it is possible to inhibit heat generation from the web and a portion of the power supply drum that is in close contact with the web. Therefore, it is possible to suppress unevenness of the anodic oxide film caused by the partial temperature increase of the web.

Regarding the second object of the present invention, in the power supply drum, the surface of the portion that is in close contact with the web is constituted of an electron conductive inorganic compound. Since the electron conductive inorganic compound has a low resistance, and is harder and better in durability than a metal, it is possible to obtain a power supply drum showing a small degree of change in contact resistance with respect to the web and a high degree of durability at the time of continuous production. Furthermore, it is possible to completely prevent the anodic oxide film from being formed on a side where the power supply drum is in close contact with the web. Consequently, at a stabilized low contact resistance, the anodic oxide film can be stably formed on one surface of the web over a long time.

Regarding the third object of the present invention, a circulator that moves the electrolytic solution present in a gap between the counter electrode and the web that is supported by the power supply drum in close contact with the web out of the gap is provided. Therefore, the electrolytic solution generating heat along with anodization can be efficiently discharged from the gap. Accordingly, it is possible to form anodic oxide film showing a high degree of film thickness uniformity and having an excellent surface condition. Moreover, it is possible to completely prevent the anodic oxide film from being formed on the side where the power supply drum is in close contact with the web. Consequently, at a stabilized contact resistance, the anodic oxide film showing a high degree of film thickness uniformity and having an excellent surface condition can be formed on one surface of the web.

Regarding the fourth object of the present invention, a power supplier that is disposed in a position above the liquid surface of the electrolytic solution and applies current to the web is provided. Accordingly, unlike the conventional method of supplying power through the shaft of a drum whose bearing mechanism is complicated, power can be supplied by a simple constitution.

Since the power supplier is disposed in a position above the liquid surface of the electrolytic solution, the rotating shaft can be placed in a position below the liquid surface of the electrolytic solution, the circumferential surface of the power supply drum can be effectively utilized for producing film, and the production efficiency can be increased.

Regarding the first to fourth objects, the web is supported by the power supply drum in close contact with the web and directly supplied with power by the power supplier from the contact surface (rear surface) on the side where the power supply drum is in close contact with the web. Accordingly, it is possible to reduce the extent of voltage drop and heat generation to an ignorable level and to increase the line speed. Consequently, even with a web having a high resistance per length in a unit width, anodic oxide film can be formed at a high speed.

Moreover, regarding the first to fourth objects, when an embodiment in which a concavity where the web runs while coming into contact with the inside thereof is disposed in the power supply drum, or an embodiment in which a guide roller that presses the protective member against the power supply drum is provided is used, it is possible to further improve water-tightness of the overlaps between the protective member and an end portion in the short-length direction of the web, and between the protective member and the portion of the power supply drum that is not in close contact with the web. Accordingly, at a more stabilized contact resistance, anodic oxide film can be formed on one surface of the web.

Further, regarding the first to fourth objects, the continuous anodizing device of the present invention is obtained by arranging in series a large number of the anodizing devices described above. Therefore, it is possible to produce film at a line speed of N times the number of arranged devices, while maintaining the surface current density in the power supply drum in each anodizing device at a maximum value not causing defectiveness in anodization. Moreover, it is possible to produce a thick AAO film having a thickness of 5 μm or greater at a high speed for a thin web made of aluminum having high resistance or for a web made of composite conductive metal foil of which at least one surface is composed of aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing an anodizing device of an embodiment for achieving the first object of the present invention.

FIG. 2 is a schematic cross-sectional view of the anodizing device shown in FIG. 1.

FIG. 3 is a graph showing the relationship between a surface pressure and a contact resistance in a power supply drum of the anodizing device of the embodiment for achieving the first object of the present invention.

FIG. 4 is a schematic perspective view showing an anodizing device of an embodiment for achieving the second object of the present invention.

FIG. 5 is a schematic cross-sectional view of the anodizing device shown in FIG. 4.

FIG. 6A is a schematic cross-sectional view showing a main part of a power supply drum in which a pinhole is present in a conductive portion (conductive material) formed on a surface of an underlaying metal constituted of an unanodizable metal, and FIG. 6B is a schematic cross-sectional view showing a main part of a power supply drum in which a cavity has been formed in the underlaying metal.

FIG. 7A is a schematic cross-sectional view showing a main part of a power supply drum in which a pinhole is present in a conductive portion (conductive material) formed on a surface of an underlaying metal constituted of an anodizable metal, and FIG. 7B is a schematic cross-sectional view showing a main part of a power supply drum in which an oxide film has been formed in a pinhole portion.

FIG. 8 is a schematic front view of a power supply drum provided with a concavity in which a web runs while coming into contact with the inside thereof.

FIG. 9 is a schematic view showing the relationship between the width and diameter of a power supply drum and the relationship between a web and a protective member.

FIG. 10 is a schematic cross-sectional view showing an example of an anodizing device provided with guide rollers.

FIG. 11 is a schematic front view of the power supply drum of FIG. 10 that is provided with guide rollers.

FIG. 12 is a schematic view of an anodizing device in the case where a potential of a counter electrode is made to exhibit a negative polarity against the ground.

FIG. 13 is a schematic view of a continuous anodizing device obtained by arranging in series a plurality of the anodizing devices of the embodiment for achieving the first to fourth objects of the present invention.

FIG. 14 is a graph showing the relationship between a running speed and an AAO film formation speed.

FIG. 15 is a schematic perspective view showing an anodizing device of an embodiment for achieving the third object of the present invention.

FIG. 16A is a schematic cross-sectional view of the anodizing device shown in FIG. 15, and FIG. 16B is schematic lateral and cross-sectional view for illustrating the action of the anodizing device shown in FIG. 15.

FIG. 17A is a schematic cross-sectional view showing a first modification example of the anodizing device shown in FIG. 15, and FIG. 17B is a schematic cross-sectional view showing a second modification example of the anodizing device shown in FIG. 15.

FIG. 18 is a schematic cross-sectional view showing a third modification example of the anodizing device shown in FIG. 15.

FIG. 19A is a schematic perspective view showing a fourth modification example of the anodizing device shown in FIG. 15, and FIG. 19B is a schematic lateral and cross-sectional view of the anodizing device shown in FIG. 19A.

FIG. 20 is a schematic perspective view showing a fifth modification example of the anodizing device shown in FIG. 15.

FIG. 21A is a schematic cross-sectional view of the anodizing device shown in FIG. 20, and FIG. 21B is a schematic lateral view for illustrating the action of the anodizing device shown in FIG. 20.

FIG. 22A is a schematic cross-sectional view showing a sixth modification example of the anodizing device shown in FIG. 15, and FIG. 22B is a schematic cross-sectional view of the anodizing device shown in FIG. 22A.

FIG. 23A is a schematic perspective view showing a seventh modification example of the anodizing device shown in FIG. 15, and FIG. 23B is a schematic cross-sectional view of the anodizing device shown in FIG. 23A.

FIG. 24A is a schematic perspective view showing an eighth modification example of the anodizing device shown in FIG. 15, and FIG. 24B is a schematic cross-sectional view showing the anodizing device shown in FIG. 24A.

FIG. 25 is a schematic perspective view showing an anodizing device of an embodiment for achieving the fourth object of the present invention.

FIG. 26 is a schematic cross-sectional view of the anodizing device shown in FIG. 25.

FIG. 27A is a schematic cross-sectional view showing a first modification example of the anodizing device shown in FIG. 25, and FIG. 27B is a schematic cross-sectional view showing a second modification example of the anodizing device shown in FIG. 25.

FIG. 28 is a schematic cross-sectional view showing a third modification example of the anodizing device shown in FIG. 25.

FIG. 29 is a schematic cross-sectional view showing a fourth modification example of the anodizing device shown in FIG. 25.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the anodizing device, the continuous anodizing device, and the film forming method of the present invention will be described in detail by using drawings.

FIG. 1 is a schematic perspective view showing an anodizing device of an embodiment for achieving a first object of the present invention, and FIG. 2 is a schematic cross-sectional view of the anodizing device of the embodiment for achieving the first object that is shown in FIG. 1.

Hereinafter, the anodizing device used in common for achieving the first to fourth objects of the present invention will be described.

As shown in FIGS. 1 and 2, an anodizing device 10 of the present invention has a power supply drum 2 which is in close contact with and supports a web made of an anodizable metal or a web 1 made of composite conductive metal foil of which at least one surface is composed of an anodizable metal (hereinafter, also called simply “web 1”), and in which at least a portion 2 a that is in close contact with the web 1 is constituted with a conductive material; a counter electrode 3 (in FIG. 1, the counter electrode is not shown to make other portions easily recognized) that is disposed to face the power supply drum 2; an electrolytic tank 5 that is filled with an electrolytic solution 4 into which a portion of the power supply drum 2 that is in close contact with and supports the web 1 and the counter electrode 3 are dipped; and a protective member 6 made of a nonconductive material that overlaps the end portions (both sides) in the short-length direction of the web 1 that is in close contact with and supported by the power supply drum 2 and a portion 2 b (2 b is a nonconductive surface) of the power supply drum 2 that is not in close contact with the web 1 so as to protect the portions from the electrolytic solution 4. The power supply drum 2 and the counter electrode 3 are connected to a power source 9, and for forming anodic oxide film, current flows via the power supply drum 2 such that the web 1 becomes an anode.

Moreover, at the upstream side of the power supply drum 2, a winding-off roll 21 carrying the web 1 as wound thereon in a roll shape is disposed, and at the downstream side thereof, a winding-up roll 22 for rewinding the web 1 which has been wound off toward the power supply drum 2 and has undergone anodization for one surface thereof is disposed. Further, at both sides of the web 1, winding-off rolls 23 each carrying the protective member 6 as wound on the relevant roll in a roll shape are disposed between the power supply drum 2 and the winding-off roll 21, and winding-up rolls 24 each for rewinding the protective member 6 are disposed between the power supply drum 2 and the winding-up roll 22 respectively, such that the protective member 6 can overlap the web 1 and the portion 2 b that is not in close contact with the web 1. Each of the winding-up rolls 22 and 24 is provided with a driver (not shown in the drawing), such that the web 1 which is in close contact with the power supply drum 2 and the protective member 6 can run together in the electrolytic solution 4 in synchronization with the circumferential speed of the power supply drum 2.

Herein, an embodiment, in which the drivers provided to the winding-up rolls 22 and 24 drive the winding-up rolls 22 and 24 respectively such that the web 1 having undergone anodization and the protective member 6 are rewound by the winding-up rolls 22 and 24 respectively, is described. However, a constitution may be employed in which the winding-up rolls 22 and 24 are freely rotatable in a simple manner and just function to send out the web 1 and the protective member 6, and winding-up rolls respectively controlled by different drivers are disposed in the downstream thereof. When this constitution is used, between the winding-up roll 22 and another winding-up roll controlled by a driver, a rinsing tank for rinsing the anodized web with water or a drying tank for performing drying after rinsing may be installed.

The power supply drum 2 itself is constituted so as to be freely rotatable in a simple manner, and by driving the drivers described above, the power supply drum 2 transports the web 1, in a state where only one surface of the web 1 is dipped into the electrolytic solution 4. Here, the power supply drum 2 may be provided with a driving source so as to rotate for itself.

The diameter of the power supply drum 2 can be appropriately selected within a range of 50 cm to 500 cm in general, though it also depends on the production scale and the film formation speed of anodization. The portion 2 a of the power supply drum 2 which is in close contact with the web 1 is constituted with a conductive material, and the portion 2 b of the power supply drum 2 which is not in close contact with the web 1 is constituted with a nonconductive material. The width of the conductive material of the power supply drum 2 which is in close contact with the web 1 is not necessarily identical to the width of the web 1 and may be set within a range that allows meandering of the web 1. The width of the conductive material is preferably 50% to 100% and more preferably 70% to 90% on the width of the web 1.

For the mechanical strength, and in order to supply electrolytic current, the underlayer of the surface of the portion 2 a of the power supply drum 2 which is in close contact with the web 1 is preferably made of a metal. In this case, the metal of the underlayer (hereinafter, also called “underlaying metal”) is preferably an anodizable metal (valve metal). As the anodizable metal, Ti, Nb, Ta, Al, and the like can be used. Among these, aluminum (Al) is most preferable as the metal of the underlayer (underlaying metal) since it has the highest conductivity and is inexpensive. As aluminum, in addition to pure aluminum, an aluminum alloy can be used, and it is preferable to use an aluminum alloy having a purity of 90% or higher in general.

For example, as in the power supply drum 2 shown in FIG. 6A, when there is a pinhole h in a conductive portion 42 (conductive material) formed on the surface of an underlaying metal 40 constituted with an unanodizable metal, if mist containing the electrolytic solution comes into contact with the underlaying metal 40, the underlaying metal 40 may dissolve gradually, and accordingly, a cavity 44 may be formed as shown in FIG. 6B.

However, as in the power supply drum 2 shown in FIG. 7A, when the pinhole h is present in the conductive portion 42 (conductive material) formed on the surface of an underlaying metal 46 constituted with an anodizable metal (valve metal), if mist containing the electrolytic solution comes into contact with the underlaying metal 46, a strong oxide film 48 is formed in the portion of the pinhole h as shown in FIG. 7B without causing dissolution of the underlaying metal 46. Accordingly, there is substantially no problem with the formation of film.

The protective member 6 is preferably composed of nonconductive rubber or metal foil covered with nonconductive rubber. In order to further improve water-tightness, a side of the protective member 6 that is in close contact with the web 1 may be coated with an adhesive material.

In order that the protective member caused to run together secures water-tightness, it is preferable to apply tension beforehand to the protective member, though it also depends on the diameter of the power supply drum 2. When the power supply drum has a large diameter, a nonconductive rubber belt with a steel core inside or the like can be preferably used.

The web 1 is a web made of an anodizable metal or is made of composite conductive metal foil of which at least one surface is composed of an anodizable metal. The web is made of aluminum, Nb, Ta, or Ti as the anodizable metal. These metals may be alloys. For example, in a case of aluminum, in addition to pure aluminum, an aluminum alloy can be used. It is preferable to use an aluminum alloy having a purity of 90% or higher in general, and when the anodic oxide film thereof is used as an insulating film, it is preferable that the film does not contain metallic Si particles as precipitates.

Examples of preferable metals to be combined with anodizable metals into a composite conductive metal foil include iron, carbon steel, stainless steel, Ti, and the like. The thickness of the web is generally within a range of 0.02 mm to 0.5 mm. Even this type of web that exhibits a high resistance per length in a unit width can be in close contact with and supported by the power supply drum, and power can be directly supplied to the web from the rear surface of the web. Accordingly, anodic oxide film can be formed at a higher speed.

Examples of the electrolytic solution 4 include aqueous solutions of acids such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, tartaric acid, malonic acid, sulfamic acid, benzenesulfonic acid and amidosulfonic acid and salts thereof and mixed solutions thereof. In order to obtain desired quality, an optimal electrolytic solution may be selected. The concentration and temperature of the electrolytic solution can be appropriately selected.

In the anodizing device 10 of FIG. 1, the protective member 6 overlaps both end portions in a short-length direction of the web 1 that is in close contact with and supported by the power supply drum 2 and the portion 2 b of the power supply drum 2 that is not in close contact with the web 1, and the web 1 that is in close contact with the power supply drum 2 can run together with the protective member 6 in the electrolytic solution 4 in synchronization with the circumferential speed of the power supply drum 2. Therefore, even if the masking film that has been conventionally required to form anodic oxide film on one surface is not used, permeation of the electrolytic solution 4 can be prevented. Moreover, since both end portions in the short-length direction of the web 1 are completely protected by the protective member 6, even when anodization is performed on a web as a combination of dissimilar metals, such as a clad material, a side reaction caused by a local cell action does not occur. Further, it is possible to completely prevent anodic oxide film from being formed on the side where the power supply drum is in close contact with the web. Accordingly, at a stabilized low contact resistance, it is possible to stably form anodic oxide film on one surface of a metal substrate at a high speed over a long period of time.

In order to further improve water-tightness between the web 1 to be overlapped and the protective member 6 by inhibiting meandering of the web 1 to be overlapped and the protective member 6, the anodizing device 10 of FIG. 1 may be embodied such that the portion of the power supply drum 2 where the web 1 and the protective member 6 run has a small diameter. This embodiment will be described using FIGS. 8 and 9. FIG. 8 is a schematic front view of a power supply drum provided with a concavity where each of the web and the protective member runs while coming into contact with the inside thereof, and FIG. 9 is a schematic view for illustrating the relationship between the width and diameter of the power supply drum and the relationship between the web and the protective member. In FIGS. 8 and 9, the same constituents as those in FIGS. 1 and 2 are marked with the same signs, and the detailed description thereof will not be repeated unless particular description is required.

As shown in FIGS. 8 and 9, the power supply drum 2 is provided with a concavity (notch) where the web 1 runs while coming into contact with the inside thereof and a concavity where the protective member 6 runs while coming into contact with the inside thereof. In FIG. 9, W₃ and D₃ indicate the total width and the drum diameter of the power supply drum 2, W₂ and D₂ indicate the width between the outer lateral ends of two protective members 6 that come into contact with the power supply drum 2 and the corresponding drum diameter, W₁ and D₁ indicate the width of the web 1 and the corresponding drum diameter, and W₀ indicates the width of the conductive material portion of the power supply drum. If the relationship among drum diameters is set to be D₃>D₂>D₁, each of the web 1 to be overlapped and the protective member 6 is inhibited from performing meandering by the concavity provided to the power supply drum 2. Moreover, if the relationship among the above widths is set to be W₃>W₂>W₁>W₀, the web 1 is overlapped by the protective member 6 with an excellent water-tightness, whereby it is possible to more effectively prevent the electrolytic solution from permeating the rear surface of the web 1. Herein, an embodiment, in which the power supply drum 2 is provided with each of the concavity where the web 1 runs while coming into contact with the inside thereof and the concavity where the protective member 6 runs while coming into contact with the inside thereof, has been described. However, an embodiment, in which the power supply drum 2 is provided only with the concavity where the web 1 runs while coming into contact with the inside thereof, may be employed.

The anodizing device 10 of FIG. 1 may be embodied such that the device is provided with guide rollers pressing the protective member 6 against the power supply drum 2. This embodiment will be described using FIGS. 10 and 11. FIG. 10 is a schematic cross-sectional view showing an example of an anodizing device provided with guide rollers, and FIG. 11 is a schematic front view of a power supply drum provided with the guide rollers of FIG. 10. As shown in FIGS. 10 and 11, an anodizing device 10 e is provided with four guide rollers 7 for pressing two protective members 6, each of which overlaps one end portion in the short-length direction of the web 1 and the portion 2 b that is not in close contact with the web 1, against the power supply drum 2. In addition, the surfaces of the guide rollers 7 have undergone insulating treatment. If such guide rollers 7 are provided, the web 1 is overlapped by the protective members 6 with a better water-tightness, and it is possible to prevent the electrolytic solution from permeating the rear surface (surface that is in close contact with the power supply drum) of the web 1.

Herein, an embodiment, in which the guide rollers 7 are disposed only in a portion of the power supply drum 2 that is dipped into the electrolytic solution 4, has been described. However, an embodiment in which the guide rollers 7 are also disposed in a portion of the power supply drum 2 that is not dipped into the electrolytic solution 4 may be employed. For example, even if the guide rollers 7 are disposed only in a portion of the power supply drum 2 that is not dipped into the electrolytic solution 4 (portion between the winding-off roll 23 for the protective member 6 and the electrolytic solution 4), meandering of the protective member 6 can be prevented. Accordingly, the web 1 and the portion 2 b that is not in close contact with the web 1 can be overlapped by the protective member 6 with an excellent water-tightness.

In anodization, a large amount of hydrogen gas is produced from the counter electrode during the reaction and reaches the anodized surface of the web by buoyancy. When gas film is formed on the anodized surface, defectiveness is caused in anodization, and accordingly, it is necessary to cause the electrolytic solution to flow inside the electrolytic tank. Method for causing the flowing is not limited and includes stirring, gas bubbling, circulating of the solution, and the like. In order to efficiently cause the flowing, it is preferable to provide a large number of through-holes to the counter electrode. The shape of the through-holes varies with the flowing mode of the electrolytic solution (when the device is small, a stirrer is selected; alternatively, when the device is big, a stream is produced in the electrolytic solution, or the solution is caused to flow by using a stirring blade or gas bubbling), but the shape can be appropriately selected from a circular shape, a square shape, a slit shape, a mesh shape, and the like. The size of each opening varies with the distance between the power supply drum and the counter electrode, but in view of applying a uniform electric field to the anodized surface, a large-sized opening is not preferable. For example, when the distance between the power supply drum and the counter electrode is 10 cm, a diameter of 2 cm or less is preferable in the case of circular openings. As the counter electrode, general materials such as carbon and aluminum are usable.

Regarding preferable flow techniques, a circulator 60 described later is the most preferable.

The waveform of the power source at the time of anodization is a direct current in general. However, it is possible to select an optimal waveform to obtain desired quality, such as an alternating current waveform obtained by direct current superposition. The current density at the time of anidization can be freely selected. For example, the current density may be continuously kept at a constant value during the treatment time or may be gradually increased. The electrolysis system at the time of anodization may be a constant-current system or a constant-voltage system.

In anodization, oxide film is formed by realizing positive-polarity potential against the counter electrode, whereupon it is preferable with respect to the potential of the counter electrode that a voltage of negative polarity against the ground is applied to the counter electrode. In this manner, the potential of the web can become a potential close to the ground potential, and the entire equipment handling the web by a roll-to-roll method can have the ground potential. In the reverse case, the entire equipment needs to have a potential against the ground. This is dangerous and also has a possibility that defectiveness may be caused in the product since abnormal discharge such as sparking occurs between the web and the equipment.

Particularly, it is more preferable to make the potential of the web identical to the ground potential and specify both the positive electrode output and negative electrode output of the power source for electrolysis to be outputs insulated from the ground. In this manner, it is possible to completely prevent abnormal discharge between the web and the equipment in the roll-to-roll region excluding the electrolytic tank. FIG. 12 is a view schematically showing this embodiment. The potential of the web 1 can become identical to the ground potential by means of placing at least one conductive roll 29 in the roll-to-roll region excluding the electrolytic tank 5 and electrically grounding the conductive roll 29.

Moreover, if a constant-current system or a constant-voltage system is used as the electrolysis system (system of causing current to flow between the power supply drum and the counter electrode), it is preferable to monitor the voltage of the power supply drum with respect to the ground potential. In this manner, it is possible to monitor the factors causing change in quality in the longitudinal direction of the anodic oxide film on the web, such as leak current caused by the temporal deterioration of water-tightness of the protective member described above or the change in contact resistance between the web and the power supply drum.

It is preferable that the counter electrode 3 is disposed on the entire surface facing the web 1 that is in close contact with the power supply drum 2 dipped into the electrolytic solution 4, such that the interval between the counter electrode 3 and the power supply drum 2 becomes almost the same in any position. The shape of the counter electrode is preferably a shape of bent plate that forms a concentric circle with the power supply drum 2. Here, if the counter electrode 3 is disposed in the electrolytic solution 4 such that the interval between the counter electrode and the power supply drum 2 is completely the same in any position, in the region where the web to be anodized initially comes into contact with the electrolytic solution 4 (hereinafter referred to as the solution-contact region) and the region where the anodized web is separated from the electrolytic solution 4 (hereinafter referred to as the solution-separation region), current concentration resulting from electric field concentration is caused, and this leads to the defectiveness in anodization. Therefore, it is preferable to take an action in advance to reduce the effective electric field. In order to reduce the effective electric field as above, the resistance of electrolytic solution may be used as a simple way. In at least one of the solution-contact region and the solution-separation region, the power supply drum and the counter electrode may be disposed having a long distance therebetween. Alternatively, in at least one of the solution-contact region and the solution-separation region, the counter electrode may be absent. As another option, the above two ways may be used concurrently.

In FIG. 2, the counter electrode is disposed such that there is a long distance between the power supply drum 2 and the counter electrode 3 in the solution-contact region and the solution-separation region. That is, an interval P₁ between the power supply drum 2 and the counter electrode 3 in the solution-contact region and an interval P₂ between the power supply drum 2 and the counter electrode 3 in the solution-separation region are larger than an interval P₃ between the power supply drum 2 and the counter electrode 3 in a central region where the web 1 is dipped into the electrolytic solution 4. Here, the intervals P₁ to P₃ are each the shortest distance connecting the power supply drum to the counter electrode. If the counter electrode is disposed in the above manner, it is possible to reduce the effective electric field and to inhibit the occurrence of defectiveness in anodization. Furthermore, FIG. 10 shows an embodiment in which the counter electrode is absent in the solution-contact region and the solution-separation region.

At the stage prior to the anodization treatment, the web is subjected to washing treatment in general. The washing treatment is for removing dirt on the aluminum surface. As a simple method, a known method such as dipping the web into an alkaline solution that has an effect of dissolving natural oxide film and removing dirt is used. Moreover, surface roughening treatment may be optionally performed. The surface roughening treatment is for forming concavities and convexities at the surface of anodic oxide film to improve the adhesiveness between the film and a layer disposed on the film. This treatment is performed by a known method such as a mechanical surface roughening method, a chemical surface roughening method, an electrochemical surface roughening method, or a combination of these. In the anodizing device of the present invention, a pretreatment tank for performing the above pretreatment and a rinsing tank for removing the pretreatment solution by washing with water may be disposed in the upstream of the winding-off roll 21.

Meanwhile, the web having undergone anodizing treatment and including AAO film formed thereon generally passes through a rinsing tank for removing the electrolytic solution by washing with water and is then subjected to drying treatment.

Next, the operation of the anodizing device of the present invention will be described with reference to FIGS. 1 and 2. First, the web 1 wound in a roll shape is wound off from the winding-off roll 21, caused to be in close contact with and supported by the power supply drum, and rewound around the winding-up roll 22. Likewise, the protective member 6 wound in a roll shape is wound off from the winding-off roll 23 and rewound around the winding-up roll 24. At this time, by the protective member 6, the end portion in the short-length direction of the web 1 that is in close contact with and supported by the power supply drum 2 is overlapped along with the portion 2 b of the power supply drum 2 that is not in close contact with the web 1, such that the electrolytic solution is prevented from permeating the rear surface of the web 1. In this state, a part of the power supply drum 2, for example, the entire portion up to the center of the drum, is dipped into the electrolytic solution 4 in the electrolytic tank 5. At this time, when the drivers are driven to cause the web 1 that is in close contact with the power supply drum 2 and the protective member 6 to run together in the electrolytic solution 4 in synchronization with the circumferential speed of the power supply drum 2, and the power source 9 of the anodizing device 10 is turned on to apply current between the power supply drum 2 and the counter electrode 3, anodic oxide film is formed on one surface of the web 1 that is not in close contact with the power supply drum 2.

A continuous anodizing device 110 shown in FIG. 13 has a constitution in which three anodizing devices 10 a, 10 b, and 10 c are arranged in series, the web 1 is wound off from the winding-off roll 21 to pass the anodizing devices 10 a, 10 b, and 10 c through delivery rolls 25 a, 26 a, 25 b, 26 b, 25 c, and 26 c and rewound around the winding-up roll 22, and the protective member 6 is wound off from the winding-off roll 23 to pass the anodizing devices 10 a, 10 b, and 10 c through delivery rolls 27 a, 28 a, 27 b, 28 b, 27 c, and 28 c and rewound around the winding-up roll 24.

A pretreatment tank 11 for pretreating the web 1 is disposed between the winding-off roll 21 and the delivery roll 25 a, and a rinsing tank 12 for rinsing the anodized web with water and a drying tank 13 for performing drying after the rinsing are disposed between the delivery roll 26 c and the winding-up roll 22. The continuous anodizing device 110 shown in FIG. 13 is embodied such that the three anodizing devices 10 a, 10 b, and 10 c connected in series use the same protective member 6. However, an embodiment may be employed in which each of the anodizing devices 10 a, 10 b, and 10 c is individually provided with the winding-off roll 23 and the winding-up roll 24.

In anodization of aluminum, a Coulombic efficiency of electrolytic oxidation is about 3 C/(cm²·μm), and a film formation speed is about 2 μm/min per flowing current at a surface current density of 100 mA/cm², though these values also depend on the electrolytic solution and the electrolysis conditions. At this time, provided that a surface current density is represented by D1 (mA/cm²), an electrolysis time by t (min), and a required thickness of AAO film is represented by H (μm), these parameters are in a relationship expressed by an equation t (min)=50×H/D1. Moreover, provided that a film formation speed is represented by S, the equation is rewritten as t=H/S because S=0.02×D1. Provided that a length of the portion of the web that is dipped into the electrolytic solution is represented by L (m), and a running speed of the web is represented by LS (m/min), these parameters are in a relationship expressed by an equation LS=L/t=0.02×L×L×D1/H=L×S/H. Accordingly, the running speed LS is proportional to L and D1 or S and inversely proportional to H.

FIG. 14 is a graph showing the relationship between the running speed and the AAO film formation speed in a case where H as the AAO thickness is 10 μm. In FIG. 14, (a), (b), and (c) indicate cases where the electrolytic tank length L is 5 m, 10 m, and 15 m respectively. The running speed LS can be increased in proportional to S as the AAO film formation speed. In the present invention, the electrolytic tank length L refers to the distance by which the power supply drum is rotationally moved in the electrolytic solution. For example, when the diameter of the power supply drum is about 3 m, if the drum is dipped to a level slightly above the center thereof, the electrolytic tank length can be 5 m. The AAO film is formed on only one surface, and the other surface remains as a metal. Therefore, anodization can be continuously performed by supplying power by the drum in the same manner. Accordingly, if N electrolytic tanks are arranged in series, the running speed can be increased N-fold. In FIG. 14, (b) and (c) show the running speeds obtained when two and three electrolytic tanks are arranged in series, respectively. The vertical axis on the right in FIG. 14 indicates the electrolytic current flowing in the running direction per 1-cm width of the web in the electrolysis device using a full dipping system described below. In the present invention, this type of current does not flow as described above, and power is directly supplied from the rear surface of the web.

In the conventional electrolysis device using a system of fully dipping a web, as described above, electrolytic current needs to flow in the running direction of the web extending from the power supply section to the electrolytic tank. At this time, provided that the electrolytic current flowing in the running direction per 1-cm width of the web is represented by D2 (A/cm), the current necessary for the growth of AAO having a required thickness in the area of the web to be dipped in the electrolytic tank per unit time is calculated by D2=LS×H×[Coulombic efficiency]×100/60=5×LS×H, from the running speed LS (m/min), the AAO thickness H (μm), and a Coulombic efficiency of 3 C/(cm²·μm). Therefore, D2 is a current irrelevant to the AAO film formation speed and the electrolytic tank length but proportional to the running speed and the AAO thickness. The values shown on the vertical axis on the right in FIG. 14 are obtained when the AAO thickness is 10 μm, so that a relationship expressed by an equation D2=50×LS is established with respect to the running speed LS as indicated by the vertical axis on the left.

Meanwhile, there is an upper limit on the current flowing in the web extending from the power supply section to the electrolytic tank. When the thickness of the aluminum foil is 100 μm, even if the foil is sufficiently cooled by being showered with water, if the current exceeds 150 A/cm, due to IR heat generation resulting from the resistance of the aluminum, thermal runaway occurs, and this leads to the risk of fusing. Accordingly, no matter how the film formation speed or the electrolytic tank length is set to perform electrolysis in FIG. 14, the electrolytic current in the width direction needs to be 150 A/cm or less, that is, the running speed needs to be 3 m/min or less. Since the IR heat generation and the limiting current of fusing of the web is determined according to the resistance per unit cross-sectional area, the thinner the aluminum foil is, the smaller the limiting current per a width of 1 cm is. Moreover, in a clad material obtained by combining a metal such as steel, stainless steel or Ti, which has a high strength and at the same time high resistance, with thin aluminum, the limiting current also decreases, and the running speed also needs to be reduced.

Also in the conventional electrolysis device using a system of fully dipping a web, it is possible in principle to increase the line speed by arranging devices in series in a multistage manner. However, when the AAO film is formed on one surface, in order to supply power on each electrolysis device, steps of sticking and peeling masking film need to be added, and this is impractical. In addition, in the electrolysis device using a full dipping system, if an indirect power supply method is used to supply power, a power supply tank is provided so as to apply voltage with polarity reverse to that of the voltage for anodization. Consequently, if power is indirectly supplied by arranging electrolytic tanks in multistage manner, a reverse voltage is applied in the power supply process to the AAO film formed by the device of the former stage, whereby abnormality such as peeling of the AAO film is caused. When the AAO film is formed on both surfaces of the web, the masking film is not necessary. However, since the AAO film has insulating properties, if this film is formed on both surfaces, multistage power supply in itself becomes impossible. Furthermore, the electrolytic current flowing in the running direction needs to be doubled as calculated above, compared to the case of forming the film on one surface, and this makes it more difficult to increase the running speed. Therefore, the continuous anodizing device of the present invention has a device constitution extremely effective in a case where AAO film having a thickness of 1 μm or more is formed on one surface of thin aluminum foil and a clad material having a high resistance.

So far, the anodizing device used in common for achieving the first to fourth objects has been described.

Hereinafter, an embodiment for achieving the first object of the present invention will be described. FIG. 3 is a graph showing the relationship between a surface pressure and a contact resistance that is established when an anodizable metal is used for the web 1 and a conductive material is used for the power supply drum 2. No matter what kind of anodizable metal is used for the web 1, and no matter what kind of conductive material is used for the power supply drum 2, almost the same relationship tends to be established.

As shown in FIG. 3, it was found that the contact resistance rapidly decreases when the surface pressure is 1,000 (Pa) or higher, and the decrease in the contact resistance is saturated and stays at an approximately constant value when the surface pressure exceeds 10,000 (Pa). Moreover, when the surface pressure is less than 1,000 (Pa), the contact resistance is high. As a result, cost of power increases, and further, the amount of heat generated increases and this leads to the risk that the temperature of the web 1 may partially increase, and unevenness may be caused in the anodic oxide film.

Based on the above knowledge, it was found that suppression of the tension applied to the web 1 makes it possible to decrease the contact resistance, whereby the present invention has been accomplished.

Provided that a tension per a width of 1 m that is applied to the web 1 is represented by T (N/m), a radius of the power supply drum 2 by R (m), and a surface pressure applied to the power supply drum 2 is represented by P (Pa: N/m²), these are in a relationship expressed by an equation T=P×R. Accordingly, in order to set the surface pressure to 1,000 (Pa) or higher, the tension T per width needs to have a value of 1,000×R (N/m) or greater.

On the other hand, even if the surface pressure exceeds 10,000 (Pa), the contact resistance does not decrease much, so it is not necessary to apply such surface pressure. When the surface pressure is 10,000 (Pa), the tension T per width which is necessary for the web 1 is 10,000×R (N/m), and the device becomes a big device having rigidity high enough to endure such a big tension, whereby cost of the device increases. Moreover, if the radius R of the power supply drum 2 increases, the required tension T per width proportionately increases more and more. Accordingly, depending on the strength of the web 1, the limit of elasticity thereof may be exceeded. Therefore, the tension T per width is preferably 10,000×R or less.

Hereinafter, an embodiment for achieving the second object of the present invention will be described. FIG. 4 is a schematic perspective view showing an anodizing device of the embodiment for achieving the second object of the present invention. FIG. 5 is a schematic cross-sectional view of the anodizing device of the embodiment for achieving the second object of the present invention shown in FIG. 4.

In an anodizing device 10 d of the embodiment for achieving the second object of the present invention, the same constituents as those of the anodizing device 10 of the embodiment for achieving the first object that is shown in FIGS. 1 and 2 will be marked with the same signs, and the detailed description thereof will not be repeated.

Generally, the surface current density in anodization is 500 mA/cm² or less, so the degree of conductivity required for the conductive portion of the power supply drum 2 is not that high. Furthermore, when the conductive material of the power supply drum 2 is a metal, if the electrolytic solution permeates the drum due to the production instability, the metal surface (surface of the conductive material) is altered, and the contact resistance becomes unstable. Even when the electrolytic solution does not permeate the drum, a large amount of mist containing the electrolytic solution is produced when electrolysis is conducted. The mist adheres to the portion 2 a (surface of the conductive material) of the power supply drum 2, which portion comes into close contact with the web 1, in an area where the portion is not in contact with the web 1, whereby the metal surface may be gradually altered. Therefore, in the power supply drum 2, the surface of the portion constituted with the conductive material that comes into close contact with the web 1 (portion 2 a that comes into close contact with the web 1) is constituted with an electron conductive inorganic compound. This electron conductive inorganic compound has a low resistance and excellent durability since the compound is harder than a metal.

As the electron conductive inorganic compound, for example, at least one kind can be used among carbon or graphite, iridium oxide, titanium nitride, titanium carbide, titanium carbonitride, silicon nitride, silicon carbide, and silicon carbonitride. In any of the power supply drums using these electron conductive inorganic compounds, the contact resistance thereof exhibits surface pressure dependency as shown in FIG. 3, and the tension T per width for the first object falls within a range of 1,000×R (N/m) to 10,000×R (N/m).

The thickness of these electron conductive inorganic compounds is preferably from about 1 μm to about 10 mm, though the thickness also varies with the desired strength or conductivity. In the power supply drum 2, the surface of the portion 2 b that is not in close contact with the web 1 is constituted with a nonconductive material. As the nonconductive material, nonconductive plastic, nonconductive rubber, and the like are preferable.

Hereinafter, an embodiment for achieving the third object of the present invention will be described. FIG. 15 is a schematic perspective view showing an anodizing device of an embodiment for achieving the third object of the present invention. FIG. 16A is a schematic cross-sectional view showing the anodizing device of the embodiment for achieving the third object that is shown in FIG. 15, and FIG. 16B is a schematic lateral view for illustrating the action of the anodizing device of the embodiment for achieving the third object that is shown in FIG. 15.

In an anodizing device 50 of the embodiment for achieving the third object, the same constituents as those in the anodizing device 10 d of the embodiment for achieving the second object that is shown in FIGS. 4 and 5 are marked with the same signs, and the detailed description thereof will not be repeated.

The anodizing device 50 of the embodiment for achieving the third object that is shown in FIGS. 15, 16A, and 16B differs from the anodizing device 10 d of FIG. 4, in terms of the constitution of the power supply drum 2, and in the respect that the anodizing device 50 is provided with a circulator 60 for moving the electrolytic solution 4, which is present in the gap d between the counter electrode 3 and the web 1 that is in close contact with and supported by the power supply drum 2, from the gap d. Since the constitution other than the above is the same as that of the anodizing device 10 d of the embodiment for achieving the second object, the detailed description thereof will not be repeated.

The circulator 60 will be described. The circulator 60 has an introducer 62 disposed in the counter electrode 3, and a supplier 64 adapted to move the electrolytic solution 4 present in the gap d from the gap d through the introducer 62.

The introducer 62 is for introducing the electrolytic solution 4 in the electrolytic tank 5 into the gap d and discharging the electrolytic solution 4 in the gap d from the gap d. The introducer 62 includes, for example, a nozzle that is attached to the opening portion disposed in the counter electrode 3. As shown in FIG. 16A, the introducer 62 is disposed in the lowermost portion of the counter electrode 3, in a direction in parallel with a rotating shaft 2 c of the power supply drum 2.

The introducer 62 is not particularly limited to nozzles, as long as it can introduce the electrolytic solution 4 in the electrolytic tank 5 into the gap d.

The supplier 64 is for supplying the electrolytic solution 4 in the electrolytic tank 5 to the introducer 62 and introducing the electrolytic solution 4 in the electrolytic tank 5 into the gap d through the introducer 62 as shown in FIG. 16B, for example. The supplier 64 is not particularly limited in terms of the constitution, as long as it can supply the electrolytic solution 4 in the electrolytic tank 5 to the introducer 62. The supplier 64 may be adapted to circulate the electrolytic solution 4 in the gap d and the electrolytic solution 4 in the electrolytic tank 5. For example, a pump or the like is used for the supplier 64.

In the circulator 60, by the supplier 64, the electrolytic solution 4 in the electrolytic tank 5 is introduced into the gap d through the introducer 62. For example, as shown in FIG. 16A, the electrolytic solution 4 present in the gap d is moved in a direction approximately in parallel with the longitudinal direction of the web 1 along the circumferential surface of the power supply drum 2, and is discharged from a first opening 30 of the gap d. As a result, it is possible to remove the electrolytic solution 4 with increased temperature that is present in the gap d from the gap d and to supply the electrolytic solution 4 in the electrolytic tank 5 which is not affected by heat generation to the gap d.

Next, the operation of the anodizing device 50 will be described with reference to FIGS. 15 and 16A. First, the web 1 wound in a roll shape is wound off from the winding-off roll 21 and caused to be in close contact with and supported by the power supply drum, and then rewound by the winding-up roll 22. Likewise, the protective member 6 wound in a roll shape is wound off from the winding-off roll 23 and rewound by the winding-up roll 24. At this time, by the protective member 6, the end portion in the short-length direction of the web 1 that is in close contact with and supported by the power supply drum 2 is overlapped along with the portion 2 b of the power supply drum 2 that is not in close contact with the web 1, such that the electrolytic solution is prevented from permeating the rear surface of the web 1. In this state, a part of the power supply drum 2, for example, the entire portion up to the center of the drum, is dipped into the electrolytic solution 4 in the electrolytic tank 5. Herein, the drivers are driven to cause the web 1 that is in close contact with the power supply drum 2 and the protective member 6 to run together in the electrolytic solution 4 in synchronization with the circumferential speed of the power supply drum 2, and the power source 9 of the anodizing device 50 is turned on to cause current to flow between the power supply drum 2 and the counter electrode 3. At this time, in the circulator 60, the electrolytic solution 4 in the electrolytic tank 5 is introduced into the gap d through the introducer 62 by the supplier 64, and the electrolytic solution 4 in the gap d is discharged from the gap d. As a result, anodic oxide film is formed on one surface (surface 1 b) of the web 1 that is not in close contact with the power supply drum 2.

The circulator 60 may be constituted such that the introducer 62 is disposed at one first opening 30 of the gap d, as in an anodizing device 50 a shown in FIG. 17A. In this case, the electrolytic solution 4 in the electrolytic tank 5 is introduced from one first opening 30 of the gap d, and the electrolytic solution 4 present in the gap d is moved in a direction opposite to the transport direction of the web 1 and a rotation direction r of the power supply drum 2 and discharged from the other first opening 30. As a result, the electrolytic solution 4 in the gap d that has a temperature increased due to heat generation resulting from anodization is removed from the gap d, and the electrolytic solution 4 in the electrolytic tank 5 is supplied to the gap d.

The introducer 62 may be disposed oppositely to that of FIG. 17A, that is to say, at the other first opening 30 of the gap d as above, and the electrolytic solution 4 may be moved along the rotation direction r and discharged from the former first opening 30 of the gap d.

The circulator 60 may be constituted such that plural introducers 62, for example, two introducers 62 are disposed, as in an anodizing device 50 b shown in FIG. 17B. In this case, one introducer 62 is disposed in the lowermost portion of the counter electrode 3 as shown in FIG. 16A, and the other is disposed at one first opening 30 of the gap d as shown in FIG. 17A. The electrolytic solution 4 in the electrolytic tank 5 is introduced from the above first opening 30 of the gap d and the lowermost portion of the counter electrode 3, and the electrolytic solution 4 present in the gap d is moved in a direction opposite to the transport direction of the web 1 and the rotation direction r of the power supply drum 2 and discharged from the other first opening 30. As a result, the electrolytic solution 4 in the gap d that has a temperature increased due to heat generation resulting from anodization is removed from the gap d, and the electrolytic solution 4 in the electrolytic tank 5 is supplied to the gap d.

The introducer 62 disposed at one first opening 30 of the gap d as shown in FIG. 17B may alternatively be disposed at the other first opening 30 of the gap d, and the electrolytic solution 4 may be discharged from the former first opening 30 of the gap d.

In addition, the number of the introducers 62 is not limited to two. Plural introducers, for example, three or more introducers 62 may be provided.

Moreover, the circulator 60 may be constituted such that as in an anodizing device 50 c shown in FIG. 18, plural counter electrodes 3 a, for example, two counter electrodes 3 a are disposed having a gap a therebetween so as to cause the lowermost portion of the power supply drum 2 to be opened, and each counter electrode 3 a is disposed such that there is a gap d between the electrode and the power supply drum 2. Each counter electrode 3 a is provided with the introducer 62, and each introducer 62 is connected to the supplier 64. Further, each counter electrode 3 a and the power supply drum 2 are connected to the power source 9.

In this case, by the supplier 64, the electrolytic solution 4 in the electrolytic tank 5 is introduced from each introducer 62 into the gap d of each counter electrode 3 a, and the electrolytic solution 4 in each gap d is discharged from the gap a and the first openings 30. As a result, the electrolytic solution 4 in the gap d that has a temperature increased due to heat generation resulting from anodization is removed from the gap d, and the electrolytic solution 4 in the electrolytic tank 5 is supplied to the gap d.

The number of the counter electrodes 3 a is not limited to two. Plural counter electrodes 3 a, for example, three or more counter electrodes 3 a may be provided.

In addition, the constitution of an anodizing device 52 shown in FIGS. 19A and 19B may be employed. In the anodizing device 52, the introducer 62 of the circulator 60 is disposed at one second opening 32 of the gap d of the counter electrode 3. Since the constitution other than the above is the same as that of the anodizing device 50 of FIG. 15, the detailed description thereof will not be repeated.

In this case, as shown in FIG. 19B, by the supplier 64, the electrolytic solution 4 in the electrolytic tank 5 is introduced from the introducer 62 into the gap d of each counter electrode 3, and the electrolytic solution 4 present in the gap d moves in a direction approximately in parallel with the short-length direction of the web 1 so as to move along the direction of the rotating shaft 2 c of the power supply drum 2 and is discharged from the other second opening 32 among the openings of the gap d. As a result, the electrolytic solution 4 in the gap d having a temperature increased due to heat generation resulting from anodization is removed from the gap d, and the electrolytic solution 4 in the electrolytic tank 5 is supplied to the gap d.

Plural introducers 62 may be provided. Moreover, a constitution may be employed in which another cover member for blocking the first openings 30 is provided, and the electrolytic solution 4 is discharged from the second openings 32.

The circulation direction of the electrolytic solution is more preferably a direction approximately in parallel with the longitudinal direction of the web. The reason is as follows.

When the electrolytic solution circulates in the short-length direction, depending on the condition, the temperature or the flow rate of the electrolytic solution changes near the introduction region of the electrolytic solution and near the opening portions in the discharge region. Accordingly, uniform film cannot be formed, and distribution is observed in the film thickness and the fine structure of the film in some cases. In this case, there is a possibility that the properties of the anodic oxide film may change. On the other hand, if the electrolytic solution circulates in the longitudinal direction, even if the above distribution is observed near the introduction region and near the opening portions in the discharge region, when the film is continuously formed while the web is being moved, the film is uniformly formed in any position in the longitudinal direction of the web on which the film has been formed.

A more preferable embodiment for causing the electrolytic solution to flow in the longitudinal direction of the web includes a technique of attaching a cover member as described below.

In addition, when the electrolytic solution is caused to flow in the longitudinal direction of the web, in the region where the web is dipped into the electrolytic solution or the region where the web is separated from the electrolytic solution, the liquid surface easily changes in level due to the flowing of the electrolytic solution. If the electrolyzed portion constantly changes in this manner, the appearance of the film is spoiled due to unevenness in the shape of streaks caused in the longitudinal direction of the web. When the above phenomenon is obvious, the film thickness exhibits unevenness and affects the properties of the anodic oxide film. As a more preferable embodiment for solving the above problem, there is a technique of providing a permeation preventer for the electrolytic solution as described below.

The constitution of an anodizing device 52 a shown in FIGS. 20, 21A, and 21B may be employed. The anodizing device 52 a is provided with first cover members 70 and is provided with a permeation preventer adapted to prevent the electrolytic solution 4 from permeating an opened area β which faces an area where the web 1 is wound around the power supply drum 2. Since the constitution other than the above is the same as that of the anodizing device 50 of FIG. 15, the detailed description thereof will not be repeated.

As shown in FIG. 21B, the anodizing device 52 a includes the first cover members 70 for blocking the second openings 32 of the gap d between the power supply drum 2 and the counter electrode 3. The first cover members 70 are fixed to the end portions of the counter electrode 3 in the direction of the rotating shaft 2 c of the power supply drum 2, respectively. Owing to the first cover members 70, the electrolytic solution 4 in the gap d is discharged from the first openings 30.

The first cover members 70 are formed of a nonconductor such as plastic like vinyl chloride or rubber.

The first cover members 70 are not limited to be fixed to the end portions of the counter electrode 3 in the direction of the rotating shaft 2 c of the power supply drum 2 as shown in FIG. 21B. For example, the members may be fixed to the inner wall of the electrolytic tank 5 so as to block the second openings 32 of the gap d.

The permeation preventer includes, for example, rollers 80 and 82 disposed above the first openings 30 of the gap d. The liquid surface of the electrolytic solution 4 in the first opening 30 on the winding-off roll 21 side is the liquid surface where the web 1 comes into contact with the electrolytic solution, and the liquid surface of the electrolytic solution 4 in the first opening 30 on the winding-up roll 22 side is the liquid surface where the web 1 is separated from the electrolytic solution.

Each of the rollers 80 and 82 is disposed such that the roller comes into contact with a surface 1 b (second surface) opposite with a contact surface 1 a (first surface) where the web 1 comes into contact with the power supply drum. Each of the rollers 80 and 82 rotates along with the transport of the web 1. Each of the rollers 80 and 82 prevents the electrolytic solution 4, which is discharged from each of the first openings 30, from flowing into the opened area β where the web 1 is not wound around the power supply drum 2. As a result, alteration or the like of the power supply drum 2 can be inhibited.

The permeation preventer may include at least one of the rollers 80 and 82. Moreover, the permeation preventer is not limited to having the rollers 80 and 82, and the rollers may be replaced by, for example, baffle plates or blade members. The baffle plates or blade members can be formed of, for example, plastic such as vinyl chloride or rubber.

Furthermore, the constitution of an anodizing device 52 b shown in FIGS. 22A and 22B may be employed. The anodizing device 52 b is provided with second cover members 72 and is provided with a permeation preventer adapted to prevent the electrolytic solution 4 from permeating the opened area β that faces an area where the web 1 is wound around the power supply drum 2. Since the constitution other than the above is the same as that of the anodizing device 50 of FIG. 15, the detailed description thereof will not be repeated.

As shown in FIGS. 22A and 22B, in the anodizing device 52 b, the second cover members 72 for blocking the second openings 32 of the gap d between the power supply drum 2 and the counter electrode 3 are disposed in both end portions of the power supply drum 2 in the direction of the rotating shaft 2 c. The second cover members 72 are each made of a flange-like member formed of a thin disk with a diameter larger than that of the power supply drum 2. Owing to the second cover members 72, the electrolytic solution 4 in the gap d is discharged from the first openings 30. The second cover members 72 can be constituted with, for example, the flange-like members each formed of a thin disk with a diameter larger than that of the power supply drum 2 that are fixed to the rotating shaft 2 c, or the annular members which are fixed to both end faces of the power supply drum 2 and protrude toward the outer periphery thereof.

The second cover members 72 just need to be able to block the second openings 32 of the gap d, and may be constituted such that they can rotate relative to the rotating shaft 2 c of the power supply drum 2 without being fixed to the power supply drum 2. For example, the second cover members 72 may have a constitution in which thin disks having a diameter larger than that of the power supply drum 2 are freely rotatable relative to the rotating shaft 2 c. When the second cover members 72 are constituted as above such that they can freely rotate relative to the rotating shaft 2 c of the power supply drum 2, even when the power supply drum 2 rotates, the second cover members 72 can each be held in a predetermined position. Accordingly, the second cover members 72 do not necessarily need to be disposed over the entire circumference of the power supply drum 2, and second cover members 72 in arc shape may be disposed in a range where the counter electrode 3 extends.

Similarly to the first cover members 70 described above, the second cover members 72 are formed of a nonconductor, for example, plastic such as vinyl chloride or rubber.

Since the constitution of the permeation preventer is the same as that of the anodizing device 52 a described above, the detailed description thereof will not be repeated.

The anodizing device 52 b is provided with the second cover members 72 for blocking the second openings 32 of the gap d and the permeation preventer for preventing the electrolytic solution 4 from permeating the opened area β of the power supply drum 2. Accordingly, the electrolytic solution 4 having generated heat along with anodization can be efficiently removed out of the gap d from the first openings 30 of the gap d, and moreover, the electrolytic solution 4 having been discharged from the first openings 30 can be prevented from permeating the opened area β of the power supply drum 2.

Further, the constitution of an anodizing device 52 c shown in FIGS. 23A and 23B may be employed. In the anodizing device 52 c, the rotating shaft 2 c of the power supply drum 2 is placed in a position below the highest level of the electrolytic solution 4, and a counter electrode 3 b extends along the circumferential surface of the power supply drum 2 for a longer length. This device is provided with third cover members 74 and further, is provided with a permeation preventer adapted to prevent the electrolytic solution 4 from permeating the opened area β that faces an area where the web 1 is wound around the power supply drum 2. Since the constitution other than the above is the same as that of the anodizing device 50 of FIG. 15, the detailed description thereof will not be repeated.

In the anodizing device 52 c, the counter electrode 3 b extends to a level above the rotating shaft 2 c. The anodizing device 52 c is provided with the third cover members 74 for blocking the second openings 32 of the gap d between the power supply drum 2 and the counter electrode 3 b. Accordingly, the electrolytic solution 4 in the gap d is discharged from the first openings 30.

Similarly to the first cover members 70, the third cover members 74 are formed of a nonconductor, for example, plastic such as vinyl chloride or rubber.

Since the permeation preventer is constituted in the same manner as in the anodizing device 52 a described above, the detailed description thereof will not be repeated.

The anodizing device 52 c is provided with the counter electrode 3 b extending to a level above the rotating shaft 2 c and the third cover members 74. Therefore, if the circulator 60 causes the electrolytic solution 4 in the electrolytic tank 5 to flow into the gap d, the electrolytic solution 4 can reach a level above the rotating shaft 2 c, whereby the highest level of the electrolytic solution 4 can be placed in a position above the rotating shaft 2 c. As a result, the portion of the web 1 dipped into the electrolytic solution can be lengthened, and the electrolytic solution 4 having generated heat along with anodization can be removed out of the gap d. Moreover, in the anodizing device 52 c, since the electrolytic solution 4 can reach the position above the rotating shaft 2 c, the portion of the web 1 dipped into the electrolytic solution can be lengthened, and the circumferential surface of the power supply drum 2 can be effectively used for film formation. Consequently, the production efficiency can be increased.

Further, the constitution of an anodizing device 52 d shown in FIGS. 24A and 24B may be employed. In the anodizing device 52 d, the rotating shaft 2 c of the power supply drum 2 is placed in a position below the highest level of the electrolytic solution 4, and the counter electrode 3 b extends along the circumferential surface of the power supply drum 2 for a longer length. This device is provided with the second cover members 72 and is provided with a permeation preventer adapted to prevent the electrolytic solution 4 from permeating the opened area β that faces an area where the web 1 is wound around the power supply drum 2. Since the constitution other than the above is the same as that of the anodizing device 50 of FIG. 15, the detailed description thereof will not be repeated.

As shown in FIGS. 24A and 24B, in the anodizing device 52 d, the counter electrode 3 b extends to a level above the rotating shaft 2 c. The device is provided with the second cover members 72 for blocking the second openings 32 of the gap d between the power supply drum 2 and the counter electrode 3 b. The second cover members 72 are disposed at both end portions of the power supply drum 2 in the direction of the rotating shaft 2 c and are each made of a flange-like member formed of a thin disk having a diameter larger than that of the power supply drum 2. Owing to the second cover members 72, the electrolytic solution 4 in the gap d is discharged from the first openings 30. The second cover members 72 can be constituted with, for example, the flange-like members each formed of a thin disk with a diameter larger than that of the power supply drum 2 that are fixed to the rotating shaft 2 c, or the annular members which are fixed to both end faces of the power supply drum 2 and protrude toward the outer periphery thereof.

As described above, the second cover members 72 just need to be able to block the second openings 32 of the gap d, and may be constituted such that they can rotate relative to the rotating shaft 2 c of the power supply drum 2 without being fixed to the power supply drum 2. For example, the second cover members 72 may have a constitution in which thin disks having a diameter larger than that of the power supply drum 2 are freely rotatable relative to the rotating shaft 2 c. When the second cover members 72 are constituted as above such that they are freely rotatable relative to the rotating shaft 2 c of the power supply drum 2, even when the power supply drum 2 rotates, the second cover members 72 can each be held in a predetermined position. Accordingly, the second cover members 72 do not necessarily need to be disposed over the entire circumference of the power supply drum 2, and second cover members 72 in arc shape may be disposed in a range where the counter electrode 3 b extends.

Similarly to the first cover members 70 described above, the second cover members 72 are formed of a nonconductor, for example, plastic such as vinyl chloride or rubber.

Since the constitution of the permeation preventer is the same as that of the anodizing device 52 a described above, the detailed description thereof will not be repeated.

In the anodizing device 52 d, the portion of the web 1 to be dipped into the electrolytic solution can be lengthened as in the anodizing device 52 c, and the electrolytic solution 4 having generated heat along with anodization can be removed out of the gap d. Also in the anodizing device 52 d, the electrolytic solution 4 can be caused to reach a level above the rotating shaft 2 c as in the anodizing device 52 c. Accordingly, the portion of the web 1 to be dipped into the electrolytic solution can be lengthened, and the circumferential surface of the power supply drum 2 can be effectively used for film formation. Consequently, the production efficiency can be increased.

As described above, the anodizing device for achieving the third object described above is provided with the circulator 60 that can remove the electrolytic solution 4, which has a temperature increased due to the heat generation caused by anodization, out of the gap d. Therefore, the electrolytic solution 4 having generated heat in the gap d between the power supply drum 2 and the counter electrode 3 can be removed outside the gap d. Consequently, anodic oxide film that exhibits a high degree of film thickness uniformity and has an excellent surface condition can be formed.

Moreover, since the anodizing device is provided with the permeation preventer, it is possible to prevent the electrolytic solution from flowing into the opened area where the web is not wound around the power supply drum and to inhibit alteration or the like of the power supply drum. As a result, anodic oxide film that exhibits a high degree of film thickness uniformity and has an excellent surface condition can be stably formed.

The anodizing device for achieving the third object described above is also constituted such that the circulator 60 is used to introduce the electrolytic solution 4 in the electrolytic tank 5 into the gap d, but the present invention is not limited thereto. For example, the anodizing device may be constituted such that opening portions are disposed in the counter electrode, and the electrolytic solution 4 in the gap d is removed by the suction either through the first openings or the second openings, or through both the first and second openings.

Hereinafter, an embodiment for achieving the fourth object of the present invention will be described. FIG. 25 is a schematic perspective view showing an anodizing device of an embodiment for achieving the fourth object of the present invention. FIG. 26 is a schematic cross-sectional view of the anodizing device of the embodiment for achieving the fourth object that is shown in FIG. 25.

In an anodizing device 90 of the embodiment for achieving the fourth object, the same constituents as those of the anodizing device 10 d shown in FIGS. 4 and 5 are marked with the same signs, and the detailed description thereof will not be repeated.

The anodizing device 90 shown in FIGS. 25 and 26 differs from the anodizing device 10 d of FIG. 4, in terms of the constitution of the power supply drum 2, and in the respect that in the portion 2 a of the power supply drum 2 that comes in close contact with the web 1 and is constituted with a metal, a power supply roll 100 (first power supply member) is disposed as a power supplier in a position above a liquid surface 4 a of the electrolytic solution 4. Since the constitution other than the above is the same as that of the anodizing device 10 d, the detailed description thereof will not be repeated.

As shown in an anodizing device 90 a shown in FIG. 27A, the power supplier may be constituted such that, for example, power supply rolls 104 and 106 (second power supply members) that come into contact with the web 1 are disposed not in the portion 2 a coming into close contact with the web 1 but in portions above the liquid surface 4 a of the electrolytic solution 4.

In this case, as shown in FIG. 27A, each of the power supply rolls 104 and 106 is disposed so as to come into contact with the surface 1 b (second surface) opposite with the contact surface 1 a (first surface) where the web 1 comes into contact with the power supply drum 2.

The power supply rolls 104 and 106 come into contact with the surface 1 b (second surface) of the web 1 such that the web 1 is interposed between the portion 2 a of the power supply drum 2 that is in close contact with the web 1 and the power supply rolls 104 and 106. When the power supply drum 2 rotates, the power supply rolls 104 and 106 rotate in a state of coming into contact with the web 1.

The power supply rolls 104 and 106 are connected to the power source 9 similarly to the power supply roll 100. Since the constitution thereof is the same as that of the power supply roll 100, the detailed description thereof will not be repeated.

In the anodizing device 90 a, current can be applied to the web 1 by the power supply rolls 104 and 106 rotating in synchronization with the rotation of the power supply drum 2. Moreover, the power supply rolls 104 and 106 are disposed on the surface 1 b (second surface) of the web 1 such that the web 1 is interposed between the power supply drum 2 (portion 2 a that is in close contact with the web 1) and these rolls, and by the power supply rolls 104 and 106, current is applied from the surface 1 b of the web 1. Therefore, the current is inhibited from flowing in the running direction (longitudinal direction) of the web 1, and this is like applying the current to the web 1 through the power supply drum 2. Consequently, though the thinner aluminum foil is, the smaller the limiting current per a width of 1 cm becomes, it is possible to apply current to the web 1 without considering the limiting current.

The power supplier may be constituted such that, for example, a power supply member 108 (second power supply member) that comes into contact with the web 1 is disposed not in the portion 2 a coming into close contact with the web 1 but in a portion above the liquid surface 4 a of the electrolytic solution 4, as in an anodizing device 90 b shown in FIG. 27B. The power supply member 108 is constituted with a sliding member.

In the anodizing device 90 b, the power supply member 108 can apply current to the web 1 while sliding on the surface 1 b of the web 1, just like the power supply rolls 104 and 106 of the anodizing device 90 a shown in FIG. 27A. Since the power supply member 108 applies current from the surface 1 b of the web 1 just like the power supply rolls 104 and 106, this is like applying current to the web 1 through the power supply drum 2. Consequently, though the thinner aluminum foil is, the smaller the limiting current per a width of 1 cm becomes, it is possible to apply current to the web 1 without considering the limiting current.

Moreover, the constitution of an anodizing device 92 shown in FIG. 28 may be employed. The anodizing device 92 is provided with a permeation preventer adapted to prevent the electrolytic solution 4 from permeating the opened area β that faces an area where the web 1 is wound around the power supply drum 2. Since the constitution other than the above is the same as that of the anodizing device 90 of FIG. 25, the detailed description thereof will not be repeated.

As shown in FIG. 28, the above permeation preventer has, for example, rollers 80 and 82 disposed in positions above the first openings 30 of the gap d. The liquid surface of the electrolytic solution 4 in the first opening 30 on the winding-off roll 21 side is the liquid surface where the web 1 comes into contact with the solution, and the liquid surface of the electrolytic solution 4 in the first opening 30 on the winding-up roll 22 side is the liquid surface where the web 1 is separated from the solution.

Each of the rollers 80 and 82 is disposed so as to come into contact with the surface 1 b (second surface) opposite with the contact surface 1 a (first surface) where the web 1 comes into contact with the power supply drum. Each of the rollers 80 and 82 rotates along with transport of the web 1. By each of the rollers 80 and 82, the electrolytic solution 4, which is discharged from each of the first openings 30, is prevented from flowing into the opened area β where the web 1 is not wound around the power supply drum 2. When there is no such permeation preventer, the solution may flow into the opened area β, and the power supply member may be wet with the electrolytic solution. This is dangerous since short circuit, current leakage, and the like may occur. Moreover, the device may be corroded by mist of the electrolytic solution that is generated during anodization, or the generated hydrogen gas may flow into the power supply section, whereby explosion may occur due to sparking and the like at the worst. The use of the permeation preventer makes it possible to inhibit these problems.

Regarding the permeation preventer, the constitution thereof is the same as in the anodizing device 52 a of FIG. 20 except for the above. Therefore, the detailed description thereof will not be repeated.

Moreover, in the anodizing device 92, the power supplier is not limited to the power supply roll 100. Instead of the power supply roll 100, for example, a power supply member 108 shown in FIG. 27 may be provided.

In addition, the constitution of an anodizing device 92 a shown in FIG. 29 may be employed. In the anodizing device 92 a, the counter electrode 3 b extends along the circumferential surface of the power supply drum 2 for a longer length. This anodizing device is provided with the circulator 60 for moving the electrolytic solution 4, which is present in the gap d between the counter electrode 3 b and the web 1 that is in close contact with and supported by the power supply drum 2, from the gap d, and is provided with a permeation preventer adapted to prevent the electrolytic solution 4 from permeating the opened area β that faces an area where the web 1 is wound around the power supply drum 2. The constitution of the anodizing device 92 a is the same as that of the anodizing device 90 of FIG. 25, except that the rotating shaft 2 c of the power supply drum 2 is placed in a position below the highest level of the electrolytic solution 4. Therefore, the detailed description thereof will not be repeated.

In the anodizing device 92 a, the counter electrode 3 b extends to a level above the rotating shaft 2 c, and the rotating shaft 2 c of the power supply drum 2 is placed in a position below the highest level of the electrolytic solution 4. That is, the highest level of the electrolytic solution 4 is above the rotating shaft 2 c. Therefore, the portion of the web 1 to be dipped can be lengthened, the circumferential surface of the power supply drum 2 can be effectively used for film formation, and the production efficiency can be increased.

In the anodizing device 92 a, the circulator 60 includes the introducer 62 disposed in the counter electrode 3 b, and the supplier 64 that moves the electrolytic solution 4 present in the gap d from the gap d through the introducer 62.

The introducer 62 is for introducing the electrolytic solution 4 in the electrolytic tank 5 into the gap d and discharging the electrolytic solution 4 in the gap d out of the gap d. The introducer 62 includes, for example, a nozzle attached to the opening portion disposed in the counter electrode 3 b. The introducer 62 is disposed in the lowermost portion of the counter electrode 3 b, in a direction in parallel with the rotating shaft 2 c of the power supply drum 2. The introducer 62 is not particularly limited to nozzles, as long as it can introduce the electrolytic solution 4 in the electrolytic tank 5 into the gap d.

The supplier 64 is for supplying the electrolytic solution 4 in the electrolytic tank 5 to the introducer 62 and introducing the electrolytic solution 4 in the electrolytic tank 5 into the gap d through the introducer 62, for example. The supplier 64 is not particularly limited in terms of the constitution, as long as it can supply the electrolytic solution 4 in the electrolytic tank 5 to the introducer 62. The supplier 64 may be adapted to circulate the electrolytic solution 4 in the gap d and the electrolytic solution 4 in the electrolytic tank 5. For example, a pump or the like is used for the supplier 64.

In the circulator 60, by the supplier 64, the electrolytic solution 4 in the electrolytic tank 5 is introduced into the gap d through the introducer 62. For example, the electrolytic solution 4 present in the gap d is moved in directions approximately in parallel with the longitudinal direction of the web 1 along the circumferential surface of the power supply drum 2, and is discharged from the first openings 30 of the gap d. As a result, it is possible to remove the electrolytic solution 4 with increased temperature that is present in the gap d from the gap d and to supply the electrolytic solution 4 in the electrolytic tank 5 which is not affected by heat generation to the gap d.

In this manner, the electrolytic solution 4 which is present in the gap d between the power supply drum 2 and the counter electrode 3 b and has the increased temperature can be removed outside the gap d. Accordingly, it is possible to form anodic oxide film showing a high degree of film thickness uniformity and having an excellent surface condition.

Moreover, the device may be constituted such that among openings of the gap d, the second openings in the direction of the rotating shaft 2 c of the power supply drum 2 are blocked with cover members. 

What is claimed is:
 1. An anodizing device, comprising: a power supply drum which is in close contact with a web made of an anodizable metal or a web made of composite conductive metal foil with at least one surface comprising an anodizable metal and as such supports the web in a state where the web is being wound around the power supply drum, and in which at least a portion that is in close contact with the web is constituted of a conductive material; a counter electrode that is disposed to face the power supply drum; an electrolytic tank that is filled with an electrolytic solution into which a portion of the power supply drum which is in close contact with and supports the web and the counter electrode are dipped; a protective member made of a nonconductive material that overlaps an end portion in a short-length direction of the web that is supported by the power supply drum in close contact with the web and a portion of the power supply drum that is not in close contact with the web so as to protect the portions from the electrolytic solution; and a driver adapted to cause the web which is in close contact with the power supply drum and the protective member to run together in the electrolytic solution in synchronization with a circumferential speed of the power supply drum, wherein provided that a tension per width that is applied to the web wound around the power supply drum is represented by T (N/m) and a radius of the power supply drum is represented by R (m), a value of the tension T per width that is applied to the web caused to run together in the electrolytic solution is 1,000×R or greater.
 2. The anodizing device according to claim 1, wherein the tension T (N/m) per width of a value ranging from 1,000×R to 10,000×R is applied to the web.
 3. The anodizing device according to claim 1, wherein in the power supply drum, a surface of the portion that is in close contact with the web is constituted of an electron conductive inorganic compound.
 4. The anodizing device according to claim 3, wherein the electron conductive inorganic compound is at least one out of carbon or graphite, iridium oxide, titanium nitride, titanium carbide, titanium carbonitride, silicon nitride, silicon carbide, and silicon carbonitride.
 5. The anodizing device according to claim 3, wherein in the power supply drum, an underlayer of the surface of the portion that is in close contact with the web is constituted of metal, and the metal of the underlayer is an anodizable metal.
 6. The anodizing device according to claim 5, wherein the anodizable metal is aluminum.
 7. The anodizing device according to claim 1, further comprising a circulator adapted to move the electrolytic solution present in a gap between the counter electrode and the web that is supported by the power supply drum in close contact with the web out of the gap.
 8. The anodizing device according to claim 7, wherein the circulator moves the electrolytic solution present in the gap in a direction approximately in parallel with a longitudinal direction of the web.
 9. The anodizing device according to claim 7, wherein an opening portion is disposed in the counter electrode, and the circulator supplies, through the opening portion, the electrolytic solution to the gap between the counter electrode and the web that is supported by the power supply drum in close contact with the web.
 10. The anodizing device according to claim 7, wherein the circulator discharges the electrolytic solution in the gap in a direction approximately in parallel with the longitudinal direction of the web.
 11. The anodizing device according to claim 7, further comprising a cover member that blocks a second opening in a direction of a rotating shaft of the power supply drum among openings of the gap, wherein by the circulator, the electrolytic solution in the gap is discharged from a first opening in a direction approximately in parallel with the longitudinal direction of the web among openings of the gap.
 12. The anodizing device according to claim 11, wherein the cover member is fixed to the electrolytic tank or the counter electrode.
 13. The anodizing device according to claim 11, wherein the cover member is fixed to the rotating shaft of the power supply drum or is relatively rotatable.
 14. The anodizing device according to claim 1, further comprising a power supplier adapted to apply current to the web, the power supplier being disposed in a position above a liquid surface of the electrolytic solution.
 15. The anodizing device according to claim 14, wherein the power supplier has a first power supply member that comes into contact with a metal portion of the power supply drum.
 16. The anodizing device according to claim 14, wherein the power supplier has a second power supply member that comes into contact with the web.
 17. The anodizing device according to claim 14, wherein the first and second power supply members are metal rolls or carbon rolls.
 18. The anodizing device according to claim 14, wherein the first and second power supply members are metal brushes or carbon brushes.
 19. The anodizing device according to claim 1, further comprising a permeation preventer adapted to prevent the electrolytic solution from permeating an opened area that faces an area where the web is wound around the power supply drum.
 20. The anodizing device according to claim 19, wherein the permeation preventer has a roller that comes into contact with a second surface of the web opposite with a first surface in contact with the power supply drum, or has a blade member that comes into contact with the second surface.
 21. The anodizing device according to claim 20, wherein the roller that comes into contact with the second surface or the blade member that comes into contact with the second surface is disposed either at a surface of the electrolytic solution where the web comes into contact with the electrolytic solution or a surface of the electrolytic solution where the web is separated from the electrolytic solution, or at both the surfaces.
 22. The anodizing device according to claim 1, wherein the rotating shaft of the power supply drum is placed in a position below the liquid surface of the electrolytic solution.
 23. The anodizing device according to claim 1, wherein the power supply drum has a concavity in which the web runs while coming into contact with an inside thereof.
 24. The anodizing device according to claim 1, further comprising a guide roller that presses the protective member against the power supply drum.
 25. The anodizing device according to claim 1, wherein the counter electrode has a large number of through-holes.
 26. The anodizing device according to claim 1, wherein an interval between the power supply drum and the counter electrode is larger either in a region where the web supported by the power supply drum comes into contact with the electrolytic solution or a region where the web is separated from the electrolytic solution, or in both the regions, than that in a central region where the web is dipped into the electrolytic solution.
 27. The anodizing device according to claim 1, wherein the protective member comprises nonconductive rubber or metal foil which is covered with nonconductive rubber.
 28. The anodizing device according to claim 1, wherein the protective member has an adhesive material on a side that comes into close contact with the web.
 29. The anodizing device according to claim 1, wherein a potential of the counter electrode exhibits a negative polarity against ground.
 30. The anodizing device according to claim 1, wherein a potential of the web is equal to a potential of the ground, and a power source for electrolysis is an output insulated from the ground.
 31. The anodizing device according to claim 29, further comprising a monitor adapted to monitor a voltage of the power supply drum with respect to the potential of the ground.
 32. A continuous anodizing device, wherein a large number of the anodizing devices according to claim 1 are arranged in series.
 33. A film forming method, wherein the anodizing device according to claim 1 is used to form an anodic oxide film on one surface of the web. 